Chiral synthesis via organoboranes. 38. Selective reductions. 48. Asymmetric reduction of trifluoromethyl ketones by B-chlorodiisopinocampheylborane in high enantiomeric purity
作者:P. Veeraraghavan Ramachandran、Aleksandar V. Teodorovic'、Herbert C. Brown
DOI:10.1016/s0040-4020(01)80530-5
日期:1993.2
respectively. The reagent reduces alkyl trifluoromethyl ketones at a rate faster than that of the aryl derivatives, while still providing the product alcohols in very high ee. Thus, 1,1,1-trifluoroacetone, 1,1,1-trifluorononan-2-one, and 1,1,1-trifluorodecan-2-one are all reduced within 4–8 h in 89% ee, 92% ee, and 91% ee, respectively. Even α-sec-alkyl trifluoromethyl ketones are handled by 1 very efficiently
我们几年前引入的(-)- B-氯二异辛基硼烷[(-)-DIP-Chloride TM,1 ]在非常高的ee中显示可以将前手性芳基和烷基全氟酮还原为相应的旋光性醇。例如,2,2,2-三氟苯乙酮,三氟乙酰基-1-萘和三氟乙酰基-2-萘在室温下rt分别在90%ee,78%ee和91%ee中被1还原。通过从戊烷中结晶出最初形成的产物,可将1-苯基-2,2,2-三氟乙醇的光学纯度提高到≥99%ee。1,1,2,2,2-五氟苯乙酮和1,1,2,2,3,3,3,-七氟丁苯酮在3 d内还原为1分别对应于92%ee和87%ee的醇。该试剂以比芳基衍生物更快的速率还原烷基三氟甲基酮,同时仍以非常高的ee提供产物醇。因此,在89%ee,92%ee中,1,1,1-三氟丙酮,1,1,1-三氟壬二-2-酮和1,1,1-三氟癸-2-酮均在4-8小时内还原和分别为ee的91%。即使α-仲烷基三氟甲基酮也非常有效地被1处理